A description will be given of a 3GPP LTE (3rd Generation Partnership Project Long Term Evolution; referred to as “LTE” hereinafter) as an exemplary mobile communication system to which the present invention can be applied.
FIG. 1 illustrates an E-UMTS (Evolved Universal Mobile Telecommunications System) network as an exemplary mobile communication system. E-UMTS is a system evolved from UMTS (Universal Mobile Telecommunications System) and fundamental standardization for the E-UMTS is currently performed by 3GPP. The E-UMTS can be regarded as an LTE system. Details of technical specifications of UMTS and E-UMTS can respectively refer to Release 7 and Release 8 of “3rd Generation Partnership Project; Technical specification Group Radio Access Network.”
Referring to FIG. 1, E-UMTS includes an Access Gateway (AG) that is located at terminals of a User Equipment (UE), an eNode B, and a network (E-UTRAN) and linked with an external network. The eNode B can simultaneously transmit multiple data streams for a broadcast service, a multicast service and/or a unicast service.
One or more cells belong to one eNode B. A cell is set to one of bandwidths of 1.25, 2.5, 5, 10, 15 and 20 MHz and provides a downlink or uplink transmission service to a plurality of UEs. Different cells may be configured such that they provide different bandwidths. An eNode B controls transmission/reception of data to/from a plurality of UEs. The eNode B signals time/frequency domains in which downlink data will be transmitted, a coding scheme, a data size, information involving Hybrid Automatic Repeat and reQuest (HARQ), etc. to a corresponding UE by transmitting downlink scheduling information with respect to the downlink data to the UE.
The eNode B signals time/frequency domains that can be used by the UE, a coding scheme, a data size, information involving HARQ, etc. to the UE by transmitting uplink scheduling information with respect to the uplink data to the UE. An interface for user traffic or control traffic transmission can be used between eNode Bs. A Core Network (CN) can be composed of an AG and a network node for user registration of a UE. The AG manages mobility of a UE based on a Tracking Area (TA) configured with a plurality of cells.
Although wireless communication technologies have been developed to reach LTE on the basis of Wideband Code Division Multiple Access (WCDMA), demands and expectations of users and common carriers continuously increase. Furthermore, wireless access technologies are constantly developing, and thus evolution of technology is required to enhance competitiveness. The evolution of technology involves reduction of cost per bit, increase in service availability, flexible use of frequency band, simple structure and open interface, appropriate power consumption of UE, etc.
Recently, 3GPP has performed standardization of a technology following LTE. This technology is referred to as “LTE-Advanced” or “LTE-A” in the specification. One of main differences between LTE and LTE-A is a system bandwidth. LTE-A aims to support a wide band of up to 100 MHz. To achieve this, carrier aggregation or bandwidth aggregation for accomplishing a broadband using a plurality of frequency, blocks is used. The carrier aggregation uses a plurality of frequency blocks as one logical frequency band to obtain a wider frequency band. The bandwidth of each frequency block can be defined on the basis of a system block bandwidth used in LTE. Each frequency block is transmitted using a component carrier.
However, LTE-A has discussed no method of generating a reference sequence for reference signal transmission in each layer when eight layers carry reference signals.